Add a separate init and connect phase, instead of always connecting in
the constructor. This allows us to be more flexible in the future with
our streams implementations.
Now that thread-local error data is handled in error, move the thread
local data out of the `threadstate` object, since it has now become
useless indirection.
Instead of having a separate type for saving state, we can re-use the
`git_error` structure. In practice, saving the error code along with the
`git_error` information has not proven necessary or useful, so it can be
removed to simplify down to re-using a single structure.
Most callers only need to _get_ error messages. Only callers implemented
more complicated functions (like a custom ODB for example) need to set
them.
(Callback users should likely ferry their own error information in their
callback payload.)
The error handling in the ssh certificate callback is straightforward.
There's no error messages from an external library that need to be
saved, we populate the error message ourselves. Since there's nothing
custom here, it does not need to use the error saving mechanism.
Callers can specify the ssh command to invoke using `core.sshcommand` or
the `GIT_SSH` environment variable. This is useful for specifying
alternate configuration, and is particularly useful for our testing
environment.
Provide both cmdline-style handling (passing it to the shell on POSIX,
or directly to CreateProcess on win32) and execv style (passing it
directly to execv on POSIX, and mangling it into a single command-line
on win32).
A transport may want to validate that it's in a sane state; when
flushing on close, don't assume that we're doing an upload-pack; send
the correct direction.
We can't reliably detect SIGPIPE on close because of platform
differences. Track `pid` and send `SIGTERM` to a function and ensure
that we can detect it.
We may want to support SSH but with a different provider that is not
libssh2. Add GIT_SSH to indicate that we have some inbuilt SSH support
and GIT_SSH_LIBSSH2 to indicate that support is via libssh2. This is
similar to how we support GIT_HTTPS and GIT_OPENSSL, for example.
since f15c8ac71a libgit unconditionally depends on secur32 on Windows
but only added it in cmake for the winhttp and schannel variants.
In case libgit is built against openssl it would fail to link.
This moves secur32 out of the https backend selection code into
the global win32 condition (and while at it also adds ws2_32 to the .pc file)
